Computer network(Topic)

Data Communication—
 Data communication, elements of DC
Data transfer from one computer to another computer or from one device to another device is
called Data communication.
 All communication neverbe consideredasa data communication.
Although the termsof communicationanddatacommunicationare commonlyused
interchangeably.We cansay that isdata communicationwhendatageneratedforcommunication
iscommunicatedina specificway.
 Elements/components ofData communication.
1. Message,
2. Sender,
3. Receiver
4. Medium,
5. Protocol.(DatatranscriptSystem)
 Methodof Data Transmission
The methodby whichdatais transferredfromone computertoanothercomputeriscalleddata
transmissionmethod.
Two typesof data transmission:
1. Paralal,
2. Serial

Data Transmission Mode
Exchange data is called Data Transmission Mode.
Based on the flow of data transfer. There are three types of Data transmission Mode.
1. Simplex,
2. Half-Duplex,
3. Full-Duplex
Simplex:
In this case of,one side of the data flow is called simplex.
Like a sending device always sends the data to another computer and the recipient
receives the data.
Example : TV,Radio etc.
Half-Duplex:
The method by which data can be transmitted from both sender and the recipient
but not at the same time is called Half-Duplex.
In this case either end of the sender and the receiver can only receive or send data at the
Same time, but data receiving and sending at the same time can’t.
Example: Wakitki.
Full-Duplex:
The method by which data is transmitted and received at the same time from both sender,
receiver is called full-duplex data transmission mode.
In this case,any end can also send data or receive data at the same time.
Like: Mobile etc.

Internet/Intranet
Internet is global network where lots of computer and electronic devices connected.
Intranet is local network where some computer or devices connected each other and share
resources and Something.
LAN  Local Area Network
Local computerscan be locatedinthe same floorof a buildingor campus.Butin thisnetworkcomputers
have to be withina certaindistance.Thisnetworkeasyandnotexpensive.
Here we can use switch,Hub,Cable.
Characteristics ofLAN
1. Computersonthisnetworkcanprovide wiredandwirelessconnection.
2. Easy to use.
3. Data transferrate 10 MB to 1000 MB.
4. LAN data transmissionrate ismuchbetterthan WAN.
5. Verysecure.
MAN  MetropolitonAreaNetwork
Thisnetworkestablishedbetweencomputersindifferentareasof large city.

Characteristics ofMAN
1. Than Range of MAN can be from10 to 30 km.
2. The cost of relatively.
3. MANs are usuallyownedbyanorganization.
WANWide AreaNetwork
Thisnetworkof computerslocatedindifferentdistance.Internetisawide areanetwork.Here use
physical line,Fiberopticcable , satellitetransmissionandmicrowave transmission.
Usedthat we can passemail,shoppingetc.
Characteristics ofWAN
1. WAN has limitedbandwidthsodatatransmissionspeedlowerthanLAN.
2. Here we can use modem.
3. Large amountof file,dataexchange.

TOPOLOGY
Designof network.
Topologydefinethe structure of networkof how all the componentsare interconnectedeachother.
Two types of topology-
(i) Physical Actual layoutof computersof cable.
(ii) Logical Actual device interconnectedinternally.
The type of topology:
(i) Mesh
(ii) Bus
(iii) Star
(iv) Ring
(v) Tree
(vi) Hybrid
Mesh
Each computerconnectedeveryothercomputer.Highlevel of redundancy.PopularisWAN.Wiringis
complicated.
Advantage of Mesh—
(i) Easilydoesnotcause verybig problemsinthisnetwork.
(ii) It has a lotmore certainlyindatacommunication.
(iii) Networkproblemscanbe solved.
Disadvantage of Mesh—
(i) Havingto put additional linksinthisnetworkincrease the cost.

BUS
Uses a truck or backbone towhichall of the computersonthe networkconnect.Systemconnecttothis
backbone usingt-trunk.Requirelesscable anddonotany otherdevice.
Advantage of Bus—
(i) Thistopologyisveryeasyto use on small size networks.
(ii) Here lesscable.So,whichsave money.
(iii) Addingandremovingcomputers,there are noproblem.
Disadvantage of Bus—
(i) The speedof data transmissionislow.
(ii) Diagnosingthe problemisverycomplex.
STAR
All computersordevicesconnectedtothe central device.ThatisswitchorHub. Each device requiresa
single connecttohub/switch.If any cable failure,thenaffectasingle device.Mostlyused.
Advantage of Star—
(i) Easy to troubleshot.
(ii) Easy to add newdevices.
(iii) Differenttype of cable canbe usedinthe same network.
Disadvantage of Star—
(i) If there is anyprobleminthe central position,itmakesthe whole networkuseless.
(ii) Thistopologyisexpensive.

RING
Data flowonthis topologyinacircular way.
Advantage of Ring—
(i) Notrequire a central device or server.
(ii) Each computeron the networkisequal important.
(iii) Althoughthe numberof computersin the networkincrease,itsefficiencyisnotaffected.
Disadvantage of Ring—
(i) If single computeriseffect,whole networkisdown.
(ii) Diagnosingprobleminanetworkiscomplex.

HYBRID
It isthe combinationof twoormore topology.
Advantage of Hybrid—
(i) If there is a problem,iteasilydiagnosed.
(ii) If any part of damaged,whole networkcannotaffected.
Disadvantage of Hybrid—
(i) Here needhubalwaysto active.
TREE
Thistopologyisextensionpartof ringand bus topology.Easilyaddnew node.
Advantage of Tree—
(i) Easilycan add newnode orremove.

Disadvantage of Tree—
(i) Thistopologyismore complex.
NetworkingDevices
Thisdevicescreates connectionbetweentwodevices.
Hub
Characteristics ofHUB—
(i) Layer-1 Device
(ii) Electrical signal orbits
(iii) Half duplex
(iv) Cannotstore MAC(MediaAccessControl Address)
(v) Alwaysbroadcast
(vi) Single collisiondomain
(vii) LAN device
(viii) Active andPassive Hub

Advantage of Hub—
(i) The price is lowerthanany othersimilardevices.
(ii) Can connectdifferentmedium.
Disadvantage of Hub—
(i) Increase networktraffic.
(ii) Data filteringisnotpossible.
(iii) There isa possibilityof interruptionindataexchange.
Bridge
Characteristics ofBridge—
That is intelligentdevice.Bridgeinspectincomingtrafficandwhetheritforwardorreject.Itis check
source and destinationMAC.
(i) Layer-2 device.
(ii) Usedto connect multiplenetwork.
(iii) Filterdatatraffic
(iv) Two collisiondomain

Switch
Characteristic of Switch—
(i) Layer-2 device
(ii) Full diplex
(iii) ContainMAC table
(iv) Firstbroadcast thenunicast& multicast
(v) Slow
(vi) Every part of switchsingle collisiondomain.
Advantage of Switch—
(i) Reduce the possibilityof interruptionsindataexchange
(ii) Here has one broadcast port
Disadvantage of Switch—
(i) The data filteringisnotpossible.
(ii) The price is higherthanhub.
(iii) The configurationiscomplex.

Router
Characteristic of Router—
(i) Layer-3 device
(ii) WAN device
(iii) Connecttwoor more network
(iv) Interworkingdevice
(v) Uses IPaddress.
Advantage of Router—
(i) Data filteringispossible
(ii) To expandbyconnectingmultiple networks.
Disadvantage of Router—
(i) Routercost more.
(ii) The router senddataslowly.
ApplicationOf CN—
1. BusinessApplication,
2. Home Application,
3. Mobile users,
BusinessApplication—
(i) Resource Sharing—
The goal isto make all programs,equipments(like printersetc),andespeciallydata,availabletoanyone
on the networkwithoutregardtothe physical locationof the resource andthe user.

(ii) CommunicationMedium—
A computernetworkcanprovide apowerful communicationmediumamongemployees.Virtuallyevery
companythat has twoor more computers now hase-mail (electronicmail),whichemployeesgenerally
use for a great deal of dailycommunication
(iii) Ecommerce—
A goal that isstartingto become more importantinbusinessesisdoingbusinesswithconsumersover
the Internet.Airlines,bookstoresandmusicvendorshave discoveredthatmanycustomerslike the
convenienceof shoppingfromhome.Thissectorisexpectedtogrow quicklyinthe future.
OSI(ISO)
OSI model full form is Open System Interconnection Model. It created in 1976.It was the first standard
model for network communication, accepted in 1980. It was created by International Organizationfor
Standardization.
It is a conceptual framework used to describe the functions of a networking system.
It has 7 layers:
1.Physical,
2.Data Link,
3.Network,
4.Transport,
5.Session,
6.Presentation,
7.Application
Here, physical – applicationworks when data is received. And application – physical works when data is
send.
 Application – session  user support layer
 Transport  heart of OSI
 Network – Physical  network support layer
Technique  Aj pher Se Test nahi dena paraga
Here, I described this 7 layers of OSI model:

1. Application:
The application layer interacted directly with the software application. This layer produced the
data, which is transfer by network.
Like: Messenger, Email.
2. Presentation:
This layer also called translation layer. Here, data change or we can say modified here like
Encryption/ Decryption.
3. Session:
This layer is responsible for establishment of connection between two devices like sender,
receiver. It called end-end process.
4. Transport:
This is heart of OSI model.This layer accepts the data from the sessionlayerand it breaks into
smaller unit. So, Transport layer also called segment layer.
5. Network:
This layer transferred one host to another host using IP address.
6. Data Link:
Here data change to bits and responsible for the host to host delivery of the data. The main
function of thislayer is to make sure data transfer is error-free from one host to another, over
the physical layer. Using MAC address.
7. Physical:
It transferred data from host to host in binary form.

TCP/IP
TCP/IPfull formisTransmissionControl Protocol andInternetProtocol andisa suite of communication
protocolsusedtointerconnectnetworkdevicesonthe internet.
The protocol that make up TCP/IP define-
 How data istransmittedacrossa network.
 How data shouldbe formattedsoothernetworksystemcanunderstandit.
Two key TCP/IP features-
 End node verification  The twoendpointof any data transferor responsible formakingsure it
was successful.
 DynamicRouting End node can transferdata overmultiple pathandthe new chosenpaththe
bestpath individual datatransfer.
The four layersof TCP/IP-
 Applicationlayer
 Host to Host/Transport
 Internet
 Networkaccess
Applicationlayerpassthe data,Transport layersegmentthe dataandpass internet.Internetmakesit
packetand passnetworkaccess.Networkaccesslayermakesbits.
TCP/IPSolve manyproblems:
 Addressing
 Routing
 Naming
 Flowandcontrol
Logical connection between layers of the TCP/IP protocol suite
TCP/IP full form Transmission Control Protocol/Internet Protocol
This model was developed and proposed by ARPA (Advance Research Project Agency). This model was
mainly created to connect Military network.

TCP/IP also called the internet layering model or internet reference model.
The protocol that make up TCP/IP define-
 How data is transmitted across a network.
 How data should be formatted so other network system can understand it.
 How to connect to two computers into internet.
TCP Characteristics
 Connection oriented
 Retransmission
 Non-real time data
 Slow compare with UDP
 Reliable
There are four layers of TCP/IP model-
Application Layer
Application layer interacts with an application program, which is the highest level of OSI model. The
applicationlayeristhe OSIlayer,whichisclosesttothe end-user.Itmeansthe OSIapplicationlayerallows
users to interact with other software application.

Transport Layer
Transportlayerbuildsonthe networklayerinordertoprovide datatransportfroma processona source
systemmachine to a processon a destinationsystem.Itis hostedusingsingle ormultiple networks,and
also maintains the quality of service functions.
It determines how much data should be sent where and at what rate. This layer builds on the message
whichare receivedfromthe applicationlayer.Ithelpsensure thatdataunitsare deliverederror-free and
in sequence.
Transport layer helps you to control the reliability of a link through flow control, error control, and
segmentation or de-segmentation.
The transportlayeralsooffersanacknowledgmentof the successful datatransmissionandsendsthe next
data in case no errors occurred. TCP is the best-known example of the transport layer.
Internet Layer
An internetlayerisathirdlayerof TCP/IPlayersof the TCP/IPmodel.Itisalso knownasa networklayer.
The main work of this layer is to send the packets from any network, and any computer still they reach
the destination irrespective of the route they take.
The Network Interface Layer
Network Interface Layer is this layer of the four-layer TCP/IP model. This layer is also called a network
access layer. It helps you to defines details of how data should be sent using the network.
It alsoincludeshowbitsshouldopticallybe signaledbyhardware deviceswhichdirectlyinterfaceswitha
network medium, like coaxial, optical, coaxial, fiber, or twisted-pair cables.
Encapsulation  Application – Physical layer Sender
De-capsulation  Physical – Application Receiver

Network Address—
It isan identifierof node orhostor device.
Two type of address—
(i) MAC
(ii) IP
IP ADDESS—
In essence,IPaddressesare the identifier thatallowsinformationtobe sentbetweendevicesona
network:theycontainlocationinformationandmake devicesaccessibleforcommunication.The
internetneedsawayto differentiate betweendifferentcomputers,routers,andwebsites.IPaddresses
provide away of doingso and forman essential partof how the internetworks.
What is an IP?
An IPaddressisa stringof numbersseparatedbyperiods.IPaddressesare expressedasasetof four
numbers — an example addressmightbe 192.158.1.38. Each numberinthe setcan range from0 to 255.
So,the full IPaddressingrange goesfrom0.0.0.0 to 255.255.255.255.
IP addressesare notrandom.Theyare mathematicallyproducedandallocatedbythe InternetAssigned
NumbersAuthority (IANA),adivisionof the InternetCorporationforAssignedNamesand
Numbers (ICANN).ICANN isanon-profitorganizationthatwasestablishedinthe UnitedStatesin1998
to helpmaintainthe security of the internetandallow ittobe usable byall.Each time anyone registers
a domainon the internet,theygothrougha domainname registrar,whopaysa small fee toICANN to
registerthe domain.
How do IP addresseswork
If you wantto understandwhya particulardevice isnotconnectinginthe wayyouwouldexpectoryou
wantto troubleshootwhyyournetworkmaynotbe working,ithelpsunderstandhow IPaddresses
work.
InternetProtocol worksthe same wayas anyotherlanguage,bycommunicatingusingsetguidelinesto
pass information.All devicesfind,send,andexchange informationwithotherconnecteddevicesusing
thisprotocol.By speakingthe same language,anycomputerinanylocationcantalkto one another.
The use of IP addressestypicallyhappensbehindthe scenes.The processworkslike this:
1. Your device indirectlyconnectstothe internetbyconnectingatfirstto a networkconnectedtothe
internet,whichthengrantsyourdevice accesstothe internet.
2. Whenyouare at home,thatnetworkwill probablybe yourInternetService Provider(ISP).Atwork,it
will be yourcompanynetwork.
3. Your IP addressisassignedtoyourdevice byyourISP.
4. Your internetactivitygoesthroughthe ISP,andtheyroute itback to you,usingyourIP address.Since
theyare givingyouaccessto the internet,itistheirrole toassignan IPaddressto yourdevice.

5. However,yourIPaddresscan change.For example,turningyourmodemorrouteronor off can change
it.Or you can contact your ISP,andtheycan change itfor you.
6. Whenyouare out and about – forexample,traveling –andyou take yourdevice withyou,yourhome IP
addressdoesnotcome withyou.This isbecause youwill be usinganothernetwork(Wi-Fi atahotel,
airport,or coffee shop,etc.) toaccessthe internetandwill be usingadifferent(andtemporary) IP
address,assignedtoyoubythe ISP of the hotel,airportorcoffee shop.
As the processimplies,there are differenttypesof IPaddresses,whichwe explore below.
CLASS OF IP ADDRESS—
There are five classof IPAddress—
1. ClassA (0-126)
2. ClassB (128-191)
3. ClassC (192-223)
4. ClassD (224-239)
5. ClassE (240-255)
127 isa lookup address.
SIGNAL
Signal isan electromagneticorlightwave whorepresentthe data.Signal transferdataone device to
anotherdevice.
There are twotypesof signals:
1. Digital
2. Analog
Digital:
Digital signal isa sequence of voltage representsinbinaryform.Thissignalsare discrete form.Digital
signalsfasterandefficient.

Analog:
Analogsignal isa continuous electricalsignal inthe formof wave.The wave isknownascarrier wave.
LINE CODING—
Line codingis the processof convertingdigital datatodigital signal.
Classificationof Line codding:
UNIPOLAR 0 V
POLAR -V/2 V/2
BIPOLAR 0 V,-V

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